Not really sure if this is a great tutorial or not but i recently made a Monster Hunter Rathian sprite and save it as my progress went on so i thought maybe it would make a decent tutorial and help some people that might not know how or were to start
il explain it here as well as in the pic
step1:if you are going to turn a pic into a sprite then find the pic you want and shrink it if need be to the size you want it to be
step2:out line the body with bright colors so its easy to see were the body parts are and try to color code them as well if you know what colors you are going to use.
step3:depending on how drastic the shrink you may want to edit it while its large and just shrink it when you are done
step4:shrink the body piece and paste it were it needs to go
step5:add all the detail and shading now so it looks good
hope this helps give people a basic idea of how you can sprite something starting from a pic